Many touchscreen panels now incorporate in-cell technology, wherein capacitive touch sensors are integrated into the display circuitry of the touchscreen panel. Such a touchscreen panel is referred to herein as an in-cell touchscreen panel and includes in-cell touch sensors and a display portion. The in-cell touch sensors comprising an in-cell touchscreen panel are designed as a matrix of transmit electrodes and sensing electrodes intersecting at nodes, wherein the transmit electrodes are coupled to control circuitry via transmit traces and the sensing electrodes are coupled to the control circuitry via receiving traces. To detect a user touch, a conventional in-cell touchscreen panel operates in a scanning mode wherein capacitance at the intersecting nodes is measured by simultaneously sampling all rows of receiving traces and then individually applying a drive signal to each of the transmit traces, one column at a time. In-cell touch sensors typically operate in sync with the display circuitry of the in-cell touchscreen panel. Therefore, the scanning time for detecting a user touch is limited to the refresh rate of the display portion of the in-cell touchscreen panel.
The number of receiving traces comprising an in-cell touchscreen panel is generally limited to no more than the number of transmit traces, and is oftentimes less than the number of transmit traces. As the number of transmit traces increases, the time required to complete the scanning mode also increases. The increased duration of the scanning process can be problematic due to the timing constraints set by the refresh rate of the display. When the scanning mode requires more time than is allowed by the refresh rate of the display, the sampling efficiency is reduced, and the touch-detection output is more susceptible to noise and may have a lower signal-to-noise ratio (SNR).